1. Technical Field of the Invention
The present invention relates to an electromagnetically operating setting device for oscillatingly movable control elements of displacement engines, in particular for flat slide valves and lift valves, comprising a spring system and two electrically operating switching magnets, by means of which an armature actuating the control element can be moved into two discrete, opposing switching positions and can be held there by one of the switching magnets, wherein the equilibrium position of the spring system lies between the two switching positions.
2. Discussion of the Related Art
Such a setting device is known from German published patent application DE-0S 30 24 109. In a setting device of this kind the control element of a displacement engine is held in the closed state by a compression spring. Another compression spring acts on an armature interacting with the control element so that the position of equilibrium of the spring system lies in the center or near the center between the end positions of the movement of the armature. The end positions of the movement of the armature are respectively located at an electrically actuated working magnet. To switch this device, one working magnet is excited and the other is switched off. Due to the force of the prestressed spring, the armature is accelerated as far as the position of equilibrium and delayed on its further path by the then determining counteracting force of the other spring. Due to the resulting friction, the armature cannot reach the opposing end position. The armature is then attracted by the tractive force of the switching magnet over the remaining distance.
In contrast to switching systems that attract the armature against the force of the spring over the entire stroke, with this system a significant reduction in the constructive size is achieved since, owing to the small air gap to be bridged, the radial dimension of the winding window can be kept small. This is especially important with respect to the use of the setting device on displacement engines.
The working stroke of such a setting device is designed in such a manner that an opening has an adequate cross-section for the largest mass flow at the control element of a displacement engine to avoid throttling. With the smaller mass flows which occur when displacement engines, and especially internal combustion engines, are operating under partial load, operating the setting device at this maximum working stroke is inefficient since the electric energy to be supplied to change the position of the control element increases as a function of the stroke of the control element. Furthermore, a decrease in the crosssection of the opening results in an increase in the velocity of flow at the control element, a state that contributes to an improvement in the multi-phase fuel induction, especially in the air/fuel mixing in internal combustion engines. However, in the prior design, the maximum stroke of the control valve that can be carried out is limited by the measurements of the setting device and by the preselected positioning in extension of the axis of the valve and thus cannot be modified.
Accordingly, it is an object of the present invention to achieve a flexible adaptation of the setting device to the respective operating conditions and simultaneously save energy with as compact dimensions as possible of the setting device and freer arrangement of the setting device in the housing, in particular in the cylinder head of an internal combustion engine.
Other objects and advantages are apparent from the specification and drawing which follow.